Although Parkinson's disease (PD) has been known for nearly two centuries, the molecular mechanisms underlying the pathogenesis of PD remain poorly understood, and currently there is no cure to stop the progression of this devastating disease. Molecular characterization of the gene products underlying the rare familial forms of PD can help delineate the pathogenic pathways associated with neurodegeneration in the common sporadic forms of PD. Recently, deletion and missense mutations in DJ-1 were identified as the genetic defects for an early-onset, autosomal recessive form of familial PD. Furthermore, DJ-1 was found to localize within a subset of pathological tau inclusions in Picks disease, Alzheimer's disease, Lewy body dementia, progressive supranuclear palsy, and frontotemporal dementia with parkinsonism linked to chromosome 17. However, little is presently known about the biological function of DJ-1 and how DJ-1 mutations cause neurodegeneration. In this project, the applicant will use a combination of biochemical, cell biological, proteomic, and molecular genetic approaches to address the following questions: What is the biochemical function of DJ-1? Does DJ-1 act in a similar cellular pathway as alpha-synuclein, parkin and UCH-L1 or in a different pathway distinct from these other familial PD genes? How do PD-linked missense mutations affect the structure and function of DJ-1 and neuronal survival? Is DJ-1 irreversibly oxidized in idiopathic PD? If so, does oxidative damage to DJ-1 contribute to the pathogenesis of sporadic PD in a manner similar to DJ-1 genetic mutations in causing familial PD? Answers to these questions will not only advance our knowledge about the normal function of DJ-1 in neuronal physiology, but should also yield novel insights into the molecular mechanism by which DJ-1 mutations lead to neurodegeneration. Completion of the proposed project should advance our understanding of PD pathogenesis, and accelerate the efforts to discover curative therapies for PD and related neurodegenerative disorders.